Such a peeling machine comprising two or more peeling rollers is disclosed in German Specification No. 2 547 863. In this Patent Specification, the peeling rollers are driven in opposite directions and their external surfaces have a rough facing, for example of abrasive powder or carborundum. For continuous operation of the peeling machine, the produce to be peeled is fed in at one end of the peeling rollers by means of a chute and the produce already situated on the peeling rollers is pushed by the incoming vegetables or fruit towards the other end and is there collected in a collecting vessel. During the conveying, the peel of the produce to be peeled is rubbed off by the rotary movement of the peeling rollers having roughened surfaces. To promote the conveyance of the produce from one end of the peeling rollers to the other, the surfaces of the peeling rollers are provided with rib-like projections, which are distributed along a helical line over the surface of the peeling rollers. For conveying the material to be peeled, it is also known (see a prospectus entitled "The new roller peeling machine for potatoes, tubers and root vegetables" by the Inventor) to provide in the roller peeling machine at least one conveying screw which can be driven independently of the peeling rollers. In the peeling operation, fresh water is continually supplied from above to the roller peeling machine by a pipe. The fresh water immediately washes away the waste and leaves the machine as waste water, which should be understood to mean fresh water containing peel waste.
In roller peeling machines in operation, the speed of the peeling rollers and of the conveying devices, for example a conveying screw, can be regulated. The most favourable setting of the speeds together with the input rate of the produce, which constitute the most important criteria governing the quantity of the peel waste and the peeling performance, is achieved by visual assessment by operating personnel. The operator judges the peeled produce leaving the machine according to visual impressions; the speed of the rollers and of the conveying screw are then regulated according to the operator's discretion. The input rate of the produce is also adjusted solely by the operator's judgement. This control, based upon feel and subjective impressions, results in that the amount of waste material that is produced by a peeling machine is almost always considerably higher than is desired and necessary. Furthermore, the inadequate adjustment of the operating variables of the peeling machine has the effect that, assuming a constant peeling result, the output of peeled produce per hour of the peeling machine is unnecessarily reduced. The same considerations apply also for the known, intermittently operating machines, such as carborundum and knife peeling machines. One or more peeling discs, provided with knives or faced with carborundum, are disposed in the machine, or peeling cones equipped in a similar manner project laterally into the machine. Here again, visual assessment of the produce to be peeled, fed in intermittently for example in batches of 20 kg each time, is all that is provided.